1. Field of the Invention
The present invention relates to a method for manufacturing a slider that is used for a hard disk drive, and particularly relates to a method for forming a camber on the air bearing surface of a slider.
2. Description of the Related Art
A hard disk drive, which is a recording medium that is high-speed, large-capacity, high-reliability and low-cost, is widely used for recording digital information. The hard disk drive has a magnetic head slider (referred to as a slider hereafter) that is provided with at least either of a write head portion for writing information to a recording medium and a read head portion for reading information from the recording medium. A read/write portion, which merges the write head portion and the read head portion, is arranged at one end of the slider. The surface of the slider that is opposite to the recording medium is called an ABS (air bearing surface).
The air bearing surface (ABS) has rail-like protrusions in order to improve flying characteristics and operating characteristics of the slider. Further, the air bearing surface is often formed into a curved surface called a crown and a camber. The crown is a curved surface in a plane that includes the depth direction (the direction along which air flows) of a slider. The camber is a curved surface in a plane that includes the width direction (the direction that is orthogonal to the direction along which the air flows) of a slider.
A lot of methods for forming the camber, which is the subject matter of the present invention, have been disclosed. Japanese Patent Laid-Open Publication No. 84312/94 (Patent Document 1) discloses a method for forming a camber in a predetermined shape by radiating laser on an element that is to be formed into a slider. Residual stress is caused in the element by forming rails and lapping the slider. The camber is formed in a predetermined shape by radiating laser on the slider from the side that is opposite to the air bearing surface, and thereby selectively removing the surface layer of the opposite surface to change the stress state of the element.
Japanese Patent Laid-Open Publication No. 110934/99 (Patent Document 2) discloses a method for forming a camber in a predetermined shape by blasting micro particles that are made of hard material onto a bar at a high speed, while protecting rails, which are formed on the air bearing surface, with a resist film for ion-milling, thereby causing compressive stress in the surface layer of the air bearing surface other than the rails.
Japanese Patent Laid-Open Publication No. 2000-3570 (Patent Document 3) discloses a process of forming grooves in a predetermined shape on a surface of a bar that is to be formed into the air bearing surface, and lapping the bar by pressing the bar against a plate having a curved surface. Since the grooves formed on the bar open and the bar bends when the bar is pressed against the lapping plate, a camber is formed with a desired curvature according to the curvature of the lapping plate.
Japanese Patent Laid-Open Publication No. 213368/99 (Patent Document 4) discloses a process of bonding a slider to a jig having a concave curved shape using an adhesive on the back surface of a surface that is to be formed into the air bearing surface, deforming the slider in a curved shape by curing the adhesive, and lapping the surface flat that is to be formed into the air bearing surface. When lapping is finished and the slider is removed from the jig, the adhesive force is released, and a camber having a predetermined curvature is formed on the air bearing surface.
Japanese Patent Laid-Open Publication No. 203051/96 (Patent Document 5) discloses a method for lapping a bar by pressing the bar against a lapping surface whose height differs at an inner peripheral portion and at an outer peripheral portion. The bar is formed in a spherical shape that extends from the inner peripheral portion to the outer peripheral portion.
Japanese Patent Laid-Open Publication No. 334643/93 (Patent Document 6) discloses a process of forming micro grooves called scribed lines which extend on the air bearing surface except for rails in a longitudinal direction of the slider. The mechanical stress, which is generated when the scribed lines are formed, makes the machining marks open on both sides thereof, and the air bearing surface is deformed in a curved shape having a camber.
In the techniques which are described in Patent Documents 2 to 6, a slider is directly machined or a lapping plate having a specific surface is used in order to form a camber. In recent years, as a hard disk drive is miniaturized in order to mount the hard disk drive on a cellular phone etc., the slider itself is miniaturized from a conventional 30-percent slider (a slider having a dimension of approximately 1.0 mm×1.235 mm×0.3 mm) to a 20-percent slider (a slider having a dimension of approximately 0.7 mm×0.85 mm×0.23 mm) and a further miniaturization has been studied. Further, a flying height has been becoming smaller and smaller in recent years, because reduction in the flying height of a slider is effective for increasing recording density of a recording medium. In order to meet those requirements, accuracy in machining operation and the lapping surface need to be enhanced in accordance with the size and flying height of a slider. However, these methods, such as machining a slider, have their limitation and may worsen the cost and yield of the product.
The technique described in Patent Document 1, which utilizes a quite different principle, i.e. radiation of laser, is less restrictive to the requirement for miniaturization and reduction in the flying height of a slider. However, there is a problem that the stress state (compressive stress) that is generated by the radiation of laser tends to be released during inspections in the manufacturing process of a hard disk or by thermal shocks during operation of the hard disk, leading to a worsened reliability for the stability of the shape.